Ultra reliable reporting of scg measurements while spcell degrades

ABSTRACT

Systems and methods for ultra reliable reporting of secondary cell group (SCG) measurements to a secondary node (SN) used in multi-radio dual connectivity (MR-DC) operation that specifically account for the possibility of SCG special cell (SpCell) degradation are disclosed herein. A user equipment (UE) may establish a signaling radio bearer (SRB) 3 with the SN. The UE may then identify that a handover condition (which may be associated with SCG SpCell degradation) for the SCG SpCell is met, and accordingly send an SCG measurement report over each of the SRB3 and an SRB1 between the UE and a master node (MN) used in the MR-DC operation. Such information received at the MN is forwarded to the SN. Accordingly, the reception of SCG measurement reports (to enable handover to a new SpCell by the SN) is not solely dependent messages on the SpCell of the SCG alone (using SRB3), improving reliability.

TECHNICAL FIELD

This application relates generally to wireless communication systems,including systems and methods for ultra reliable reporting of secondarycell group (SCG) measurements when using multi-radio dual connectivity(MR-DC).

BACKGROUND

Wireless mobile communication technology uses various standards andprotocols to transmit data between a base station and a wireless mobiledevice. Wireless communication system standards and protocols caninclude the 3rd Generation Partnership Project (3GPP) long termevolution (LTE) (e.g., 4G) or new radio (NR) (e.g., 5G); the Instituteof Electrical and Electronics Engineers (IEEE) 802.16 standard, which iscommonly known to industry groups as worldwide interoperability formicrowave access (WiMAX); and the IEEE 802.11 standard for wirelesslocal area networks (WLAN), which is commonly known to industry groupsas Wi-Fi. In 3GPP radio access networks (RANs) in LTE systems, the basestation can include a RAN Node such as a Evolved Universal TerrestrialRadio Access Network (E-UTRAN) Node B (also commonly denoted as evolvedNode B, enhanced Node B, eNodeB, or eNB) and/or Radio Network Controller(RNC) in an E-UTRAN, which communicate with a wireless communicationdevice, known as user equipment (UE). In this disclosure, RAN nodes ofLTE systems may sometimes be referred to as LTE nodes. In fifthgeneration (5G) wireless RANs, RAN Nodes can include a 5G Node, NR node(also referred to as a next generation Node B or g Node B (gNB)).

RANs use a radio access technology (RAT) to communicate between the RANNode and UE. RANs can include global system for mobile communications(GSM), enhanced data rates for GSM evolution (EDGE) RAN (GERAN),Universal Terrestrial Radio Access Network (UTRAN), and/or E-UTRAN,which provide access to communication services through a core network.Each of the RANs operates according to a specific 3GPP RAT. For example,the GERAN implements GSM and/or EDGE RAT, the UTRAN implements universalmobile telecommunication system (UMTS) RAT or other 3GPP RAT, theE-UTRAN implements LTE RAT, and NG-RAN implements 5G RAT. In certaindeployments, the E-UTRAN may also implement 5G RAT.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

To easily identify the discussion of any particular element or act, themost significant digit or digits in a reference number refer to thefigure number in which that element is first introduced.

FIG. 1 illustrates an EN-DC architecture according to embodimentsherein.

FIG. 2 illustrates an NR-DC architecture according to embodimentsherein.

FIG. 3 illustrates a flow diagram of a failure of SCG measurementreports from a UE to reach an SN on SRB3 because of SCG SpCelldegradation when the UE is operating in an NR-DC mode, according to anembodiment.

FIG. 4 illustrates a flow diagram of a failure of SCG measurementreports from a UE to reach an SN on SRB3 because of SCG SpCelldegradation when the UE is operating in an EN-DC mode, according to anembodiment.

FIG. 5 illustrates a flow diagram of a failure of SCG measurementreports from a UE to reach an SN on SRB3 because of SCG SpCelldegradation when the UE is operating in an NR-DC mode, according to anembodiment.

FIG. 6 illustrates a flow diagram of a failure of SCG measurementreports from a UE to reach an SN on SRB3 because of SCG SpCelldegradation when the UE is operating in an EN-DC mode, according to anembodiment.

FIG. 7 illustrates a flow diagram of a system using NR-DC that isconfigured to send SCG measurement reports to both an MN and an SN inresponse to a handover condition associated with the SN and when SRB3 isconfigured between a UE and the SN, according to an embodiment.

FIG. 8 illustrates a flow diagram of a system using EN-DC that isconfigured to send SCG measurement reports to both an MN and an SN inresponse to a handover condition associated with the SN and when SRB3 isconfigured between a UE and the SN, according to an embodiment.

FIG. 9 illustrates a flow diagram of a system using NR-DC that isconfigured to send SCG measurement reports to both an MN and an SN inresponse to a handover condition associated with the SN and when SRB3 isconfigured between a UE and the SN, according to an embodiment.

FIG. 10 illustrates a flow diagram of a system using EN-DC that isconfigured to send SCG measurement reports to both an MN and an SN inresponse to a handover condition associated with the SN and when SRB3 isconfigured between a UE and the SN, according to an embodiment.

FIG. 11 illustrates a method of a UE operating in an MR-DC mode with anMN and an SN, according to an embodiment.

FIG. 12 illustrates a method of an SN operable with a UE using an MR-DCmode with an MN and the SN, according to an embodiment.

FIG. 13 illustrates a UE in accordance with one embodiment.

FIG. 14 illustrates a network node in accordance with one embodiment.

FIG. 15 illustrates components in accordance with one embodiment.

DETAILED DESCRIPTION

Multi-radio dual connectivity (MR-DC) is a generalization ofIntra-E-UTRA dual connectivity (DC), where a multiple Rx/Tx capable UEmay be configured to utilize resources provided by two different nodes,one providing NR access and the other one providing either E-UTRA (LTE)or NR access. One node may act as a master node (MN) and the other mayact as a secondary node (SN). The MN and SN may be connected via anetwork interface, and at least the MN is connected to the core network.The MN and/or the SN may be operated with shared spectrum channelaccess.

The UE can access the network using either one network node or using twodifferent nodes with various MR-DC modes. Examples of possible MR-DCmodes include an E-UTRA-NR dual connectivity (EN-DC) mode and NR-NR dualconnectivity (NR-DC) mode. In these MR-DC modes, the UE may communicatewith the MN using one or more cells of a master cell group (MCG) that isavailable/provided by the MN, and the UE may communicate with the SRusing one or more cells of a secondary cell group (SCG) that is providedby the SN. Each of the MCG and the SCG communicate with the UE usingrespectively one or more cells that includes at least a respectivespecial cell (SpCell), with the SpCell of the MCG being referred tosometimes as a PCell and the SpCell of the SCG being referred tosometimes as a PSCell.

FIG. 1 illustrates an EN-DC architecture 100 according to embodimentsherein. The EN-DC architecture 100 includes an E-UTRAN 102 and an EPC104. The E-UTRAN 102 supports MR-DC via EN-DC, in which a UE (in FIG. 1,the UE 106) is connected to one eNB that acts as a MN (in FIG. 1, theeNB 108) and one en-gNB (in FIG. 1, the en-gNB 112) that acts as a SN.An en-gNB such as the en-gNB 112 may be a node that provides NR userplane and control plane protocol terminations towards the UE 106, andmay act as a SN in EN-DC. In FIG. 1, the EPC 104 may comprise one ormore Mobility Management Entity/Serving Gateways (MME/S-GWs), such as anMME/S-GW 118 and an MME/S-GW 116. By way of example, the E-UTRAN 102 maycomprise the eNB 108, an eNB 110, the en-gNB 112, and an en-gNB 114.Each of the eNB 108 and the eNB 110 may be connected to the EPC 104 viaone or more S1 interfaces 120 and to one or more en-gNBs via one or moreX2 interfaces 124. Each of the en-gNB 112 and the en-gNB 114 may beconnected to the EPC 104 via one or more S1-U interfaces 122. The en-gNB112 and the en-gNB 114 may be connected to one another through an X2-Uinterface 126.

FIG. 2 illustrates an NR-DC architecture 200 according to embodimentsherein. By way of example, the NR-DC architecture 200 of FIG. 2illustrates a UE 202, a gNB (MN) 204, a gNB (SN) 206, and the 5G corenetwork (5GC) 208. In NR-DC, a UE 202 is connected to a first gNB (MN)204 that acts as an MN and a second gNB (SN) 206 that acts as an SN. ThegNB (MN) 204 is connected to the 5GC 208 via an NG interface 210, andconnected to the gNB (SN) 206 via an Xn interface 212. Further, the gNB(SN) 206 may be connected to the 5GC 208 via an NG-U interface 214 insome embodiments.

Signaling data attendant to the use of MR-DC may be carried using one ormore signaling radio bearers (SRBs) from the UE to one of MN or the SN.An SRB may be used during connection establishment to establish radioaccess bearers (RABs), and may then further be used to deliver signalingwhile the UE is on the connection. That signaling may be related to themanagement of the connection. For example, SRBs may further be used toperform a handover, perform and/or report measurements, handle areconfiguration or a release, etc.

An SRB1 may be configured for use between the UE and the MN. SRB1 may beused for radio resource control (RRC) messages (including piggybackednon-access stratum (NAS) messages) as well as for NAS messages prior tothe establishment of an SRB2. This signaling may occur using a dedicatedcontrol channel (DCCH).

An SRB2 may be configured for use between the UE and the MN. SRB2 may beused for RRC messages which include logged measurement information. Thissignaling may occur using a DCCH. Note that SRB2 has a lower prioritythan SRB1, and may be configured by the network after an access stratum(AS) security activation has occurred.

An SRB3 may be configured for use between the UE and the SN. SRB3 may beused for specific RRC messages when the UE is in an EN-DC or an NR-DCmode, and may use a DCCH. In cases involving EN-DC and NR-DC to bediscussed herein, SRB3 can be used, for example, for measurementconfiguration and reporting; for UE assistance (re)configuration andreporting for power savings; to (re)configure medium access control(MAC), radio link control (RLC), physical layer, and radio link failure(RLF) timers and constants of an SCG configuration; to reconfigurepacket data convergence protocol (PDCP) for data radio bearers (DRBs)associated with the SN key (S-K_(gNB)) or SRB3; to reconfigure servicedata adaptation protocol (SDAP) for DRBs associated with S-K_(gNB) inEN-DC and NR-DC; and to add/modify/release conditional SpCell of a SCG(PSCell) change configurations, provided that the (re)configuration doesnot require any MN involvement. In EN-DC and NR-DC, each of measConfig,radioBearerConfig, conditionalReconfiguration, otherConfig, and/orsecondaryCellGroup may be included in an RRCReconfigurationsent/received via SRB3.

In some embodiments of wireless communications systems using MR-DC(e.g., using EN-DC or NR-DC), it may be that while the UE is operatingin the MR-DC mode with SRB3 configured, the UE sends any SCG measurementreports on the SRB3. For example, the UE may be utilizing a SCG of theSN by communicating on (at least) the SpCell of the SCG (where the SCGmay be made of the SpCell and zero or more additional cells, which theUE may also be using for sending/receiving data to/from the SN). TheseSCG measurement reports may allow the SN to react (e.g., perform ahandover of the UE to another SpCell of a target node) to changing SCGcell conditions. It may be that, for example, a standard for a wirelesscommunication system defines some or all this behavior at the UE and/orSN.

Such measurement reports may be configured to be sent on the SpCell ofthe SCG. Accordingly, when the SpCell of the SCG begins to degrade, theprobability of such an SCG measurement report on SRB3 being received atthe SN also reduces. If the SCG measurement report reflecting thedegradation is not received at the SN, then the SN may not appropriatelyreact (e.g., perform handover to another SpCell) to the degrading natureof the SpCell (because it remains uninformed of the degradation). Thismay result in SCG failure from the point of view of the UE (e.g., an RLFwith the SpCell of the SCG), potentially leading to the disruption ofany services to the UE that were being provided to the UE through theSN.

FIG. 3 illustrates a flow diagram 300 of a failure of SCG measurementreports from a UE to reach an SN on SRB3 because of SCG SpCelldegradation when the UE is operating in an NR-DC mode, according to anembodiment. In FIG. 3, the UE functionality has been split into thefunctionalities of the UE-MCG 302, which illustrates the functions ofthe UE as they relate to the MN/MCG, and the UE-SCG 304, whichillustrates the functions of the (same) UE as they relate to the SN/SCG.The flow diagram 300 also includes an SN 306 and an MN 308 which are incommunication with the UE according to an NR-DC mode as previouslydescribed (with both the MN 308 and the SN 306 being NR nodes).

The flow diagram 300 illustrates the configuration 310 of an SRB1 and anSRB2 at the UE-MCG 302. The flow diagram 300 further illustrates theconfiguration 312 of an SRB3 at the UE-SCG 304. Because of the priorconfiguration 312 of SRB3, it may be that the UE is to make the SCGmeasurement reports 314 on SRB3, between the UE-SCG 304 and the SN 306.As illustrated, at some point in time the UE (at the UE-SCG 304)experiences the SCG SpCell degradation 316. As part of its operation,the UE-SCG 304 might attempt provide the SN 306 with a SCG measurementreport that reflects this degradation, which would ultimately result inthe SN 306 to reacting to the SCG SpCell degradation 316 (e.g., via ahandover to use another cell of a target node (which may be the SN or adifferent node altogether) as an SpCell). However, in the case of theflow diagram 300, the SCG measurement reports/retransmissions 318 thatwould normally be used for this purpose (and which are transmitted onthe SCG SpCell) do not reach the SN 306 due to the SCG SpCelldegradation 316. This is represented by the use of dotted lines on theSCG measurement reports/retransmissions 318.

The flow diagram 300 further illustrates a SCG failure 320 due to SCGSpCell RLF. Eventually, the failure to communicate to the SN 306 (e.g.,after a certain amount of time with no messaging from the SN 306), theUE will recognize a SCG failure 320 condition and send SCG failureinformation 322 to the MN 308.

Note that the determination of the UE of the SCG failure 320 may notoccur immediately with/after the SCG measurement reports/retransmissions318 fail to be received, but rather it may take some time after thebeginning of the set of SCG measurement reports/retransmissions 318before the UE concludes that the SCG failure 320 has occurred and thensends the SCG failure information 322. During this time, services fromthe network to the UE on the SN 306 may have already been substantiallyimpacted.

FIG. 4 illustrates a flow diagram 400 of a failure of SCG measurementreports from a UE to reach an SN on SRB3 because of SCG SpCelldegradation when the UE is operating in an EN-DC mode, according to anembodiment. In FIG. 4, the UE functionality has been split into thefunctionalities of the UE-MCG 402, which illustrates the functions ofthe UE as they relate to the MN/MCG, and the UE-SCG 404, whichillustrates the functions of the (same) UE as they relate to the SN/SCG.The flow diagram 400 also includes an SN 406 and an MN 408 which are incommunication with the UE according to an EN-DC mode as previouslydescribed (with the MN 408 being an LTE node and the SN 406 being an NRnode).

The flow diagram 400 illustrates the configuration 410 of an SRB1 and anSRB2 at the UE-MCG 402. The flow diagram 400 further illustrates theconfiguration 412 of an SRB3 at the UE-SCG 404. Because of the priorconfiguration 412 of SRB3, it may be that the UE is to make the SCGmeasurement reports 414 on SRB3, between the UE-SCG 404 and the SN 406.As illustrated, at some point in time the UE (at the UE-SCG 404)experiences the SCG SpCell degradation 416. As part of its operation,the UE-SCG 404 might attempt provide the SN 406 with a SCG measurementreport that reflects this degradation, which would ultimately result inthe SN 406 to reacting to the SCG SpCell degradation 416 (e.g., via ahandover to use another cell of a target node (which may be the SN or adifferent node altogether) as a SpCell). However, in the case of theflow diagram 400, the SCG measurement reports/retransmissions 418 thatwould normally be used for this purpose (and which are transmitted onthe SCG SpCell) do not reach the SN 406 due to the SCG SpCelldegradation 416. This is represented by the use of dotted lines on theSCG measurement reports/retransmissions 418.

The flow diagram 400 further illustrates an SCG failure 420 due to SCGSpCell RLF. Eventually, the failure to communicate to the SN 406 (e.g.,after a certain amount of time with no messaging from the SN 406), theUE will recognize a SCG failure 420 condition and send SCG failureinformation 422 to the MN 408.

Note that the determination of the UE of the SCG failure 420 may notoccur immediately with/after the SCG measurement reports/retransmissions418 fail to be received, but rather it may take some time after thebeginning of the set of SCG measurement reports/retransmissions 418before the UE concludes that the SCG failure 420 has occurred and thensends the SCG failure information 422. During this time, services fromthe network to the UE on the SN 406 may have already been substantiallyimpacted.

It has been recognized that cases where measurement reports areconditionally triggered at the UE can also be affected when the SpCellof the SCG begins to degrade. For example, a UE may be configured totrigger an SCG measurement report (Event A3) on SRB3 when the currentSCG SpCell has a power level that is lower than a neighbor cell by athreshold amount (an A3 condition). This SCG measurement report (EventA3) contains the power level of the SCG SpCell and the power level ofthe neighbor cell, and indicates the existence of the A3 conditionbetween the SCG SpCell and the neighbor cell (e.g., through theinclusion in the SCT measurement report of a measurement ID that isknown to the network to correspond to the A3 condition). Upon receivingthis SCG measurement report, the SN 506 recognizes the A3 condition asbetween the SCG SpCell and the neighbor cell and initiates a handover tothe neighbor cell. However, it may be that the A3 condition was causedby SCG SpCell degradation, and that the SCG SpCell has degraded to theextent that the SCG measurement report (Event A3) does not reach the SN.If this SCG measurement report (Event A3) reflecting the A3 condition isnot received at the SN, then the SN may not appropriately react (e.g.,perform handover to the neighbor cell) to the A3 condition (because itremains uninformed of the A3 condition). If the SCG SpCell continues todegrade, this may eventually result in SCG failure from the point ofview of the UE (e.g., an RLF with the SCG SpCell), potentially leadingto the disruption of any services to the UE that were being provided tothe UE through the SN.

FIG. 5 illustrates a flow diagram 500 of a failure of SCG measurementreports from a UE to reach an SN on SRB3 because of SCG SpCelldegradation when the UE is operating in an NR-DC mode, according to anembodiment. In FIG. 5, the UE functionality has been split into thefunctionalities of the UE-MCG 502, which illustrates the functions ofthe UE as they relate to the MN/MCG, and the UE-SCG 504, whichillustrates the functions of the (same) UE as they relate to the SN/SCG.The flow diagram 500 also includes an SN 506 and an MN 508 which are incommunication with the UE according to an NR-DC mode as previouslydescribed (with both the MN 508 and the SN 506 being NR nodes).

The flow diagram 500 illustrates the configuration 510 of an SRB1 and anSRB2 at the UE-MCG 502. The flow diagram 500 further illustrates theconfiguration 512 of an SRB3 at the UE-SCG 504. As illustrated, thetrigger 514 for a SCG measurement report (Event A3) 516 then occurs. Inthe case of the trigger 514, the SCG SpCell has degraded, causing apower of a neighbor cell to be better than the power of the SCG SpCellby an offset or threshold amount. Because of the prior configuration 512of SRB3, it may be that the UE is to make the responsive SCG measurementreport (Event A3) 516 on SRB3, between the UE-SCG 504 and the SN 506.However, in the case of the flow diagram 500, the SCG measurement report(Event A3) 516 (and any follow on SCG measurement reports (EventA3)/retransmissions 518) which are transmitted on the SCG SpCell do notreach the SN 506 due to the SCG SpCell degradation. This is representedby the use of dotted lines on the SCG measurement report (Event A3) 516and the SCG measurement reports (Event A3)/retransmissions 518.

The flow diagram 500 further illustrates a SCG failure 520 due to SCGSpCell RLF. Eventually, the failure to communicate to the SN 506 (e.g.,after a certain amount of time with no messaging from the SN 506), theUE will recognize a SCG failure 520 condition and send SCG failureinformation 522 to the MN 508.

Note that the determination of the UE of the SCG failure 520 may notoccur immediately with/after the SCG measurement report (Event A3) 516and/or the SCG measurement reports (Event A3)/retransmissions 518 failto be received, but rather it may take some time after the beginning ofthe SCG measurement report (Event A3) 516 and/or the SCG measurementreports (Event A3)/retransmissions 518 before the UE concludes that theSCG failure 520 has occurred and then sends the SCG failure information522. During this time, services from the network to the UE on the SN 506may have already been substantially impacted.

FIG. 6 illustrates a flow diagram 600 of a failure of SCG measurementreports from a UE to reach an SN on SRB3 because of SCG SpCelldegradation when the UE is operating in an EN-DC mode, according to anembodiment. In FIG. 6, the UE functionality has been split into thefunctionalities of the UE-MCG 602, which illustrates the functions ofthe UE as they relate to the MN/MCG, and the UE-SCG 604, whichillustrates the functions of the (same) UE as they relate to the SN/SCG.The flow diagram 600 also includes an SN 606 and an MN 608, which are incommunication with the UE according to an EN-DC mode as previouslydescribed (with the MN 608 being an LTE node and the SN 606 being an NRnode).

The flow diagram 600 illustrates the configuration 610 of an SRB1 and anSRB2 at the UE-MCG 602. The flow diagram 600 further illustrates theconfiguration 612 of an SRB3 at the UE-SCG 604. As illustrated, thetrigger 614 for a SCG measurement report (Event A3) 616 then occurs. Inthe case of the trigger 614, the SCG SpCell has degraded, causing apower of a neighbor cell to be better than the power of the SCG SpCellby an offset or threshold amount. Because of the prior configuration 612of SRB3, it may be that the UE is to make the responsive SCG measurementreport (Event A3) 616 on SRB3, between the UE-SCG 604 and the SN 606.However, in the case of the flow diagram 600, the SCG measurement report(Event A3) 616 (and any follow on SCG measurement reports (EventA3)/retransmissions 618) which are transmitted on the SCG SpCell do notreach the SN 606 due to the SCG SpCell degradation. This is representedby the use of dotted lines on the SCG measurement report (Event A3) 616and the SCG measurement reports (Event A3)/retransmissions 618.

The flow diagram 600 further illustrates a SCG failure 620 due to SCGSpCell RLF. Eventually, the failure to communicate to the SN 606 (e.g.,after a certain amount of time with no messaging from the SN 606), theUE will recognize a SCG failure 620 condition and send SCG failureinformation 622 to the MN 608.

Note that the determination of the UE of the SCG failure 620 may notoccur immediately with/after the SCG measurement report (Event A3) 616and/or the SCG measurement reports (Event A3)/retransmissions 618 failto be received, but rather it may take some time after the beginning ofthe SCG measurement report (Event A3) 616 and/or the SCG measurementreports (Event A3)/retransmissions 618 before the UE concludes that theSCG failure 620 has occurred and then sends the SCG failure information622. During this time, services from the network to the UE on the SN 606may have already been substantially impacted.

FIG. 7 illustrates a flow diagram 700 of a system using NR-DC that isconfigured to send SCG measurement reports to both an MN and an SN inresponse to a handover condition associated with the SN and when SRB3 isconfigured between a UE and the SN, according to an embodiment. In FIG.7, the UE functionality has been split into the functionalities of theUE-MCG 702, which illustrates the functions of the UE as they relate tothe MN/MCG, and the UE-SCG 704, which illustrates the functions of the(same) UE as they relate to the one or more SNs/SCGs. The flow diagram700 also includes an MN 706 and a source SN 708 which at the beginningof the flow diagram 700 are in communication with the UE according to anNR-DC mode as previously described (with both the MN 706 and the sourceSN 708 being NR nodes). By the end of the flow diagram 700, the sourceSN 708 will handover to the target SN 710. Note that in some cases, itis anticipated that the source SN 708 and the target SN 710 may be thesame NR node, while in other cases the source SN 708 and the target SN710 may be different NR nodes.

The flow diagram 700 illustrates the configuration 712 of an SRB1 and anSRB2 at the UE-MCG 702. The flow diagram 700 further illustrates theconfiguration 714 of an SRB3 at the UE-SCG 704. Because of the priorconfiguration 714 of SRB3, it may be that the UE is to make the SCGmeasurement reports 716 on SRB3, between the UE-SCG 704 and the sourceSN 708.

The flow diagram 700 then illustrates that the SpCell of the SCG startsdegrading, which causes the handover condition 718. Examples of ahandover conditions as used in the flow diagram 700 may include that anout-of-sync (OOS) counter begins incrementing, or that a T310 timer isrunning at the UE. For example, as the SpCell of the SCG degrades, theUE may begin to fall out of synchronization with it. This is detected bylower layers at the UE, which send OOS indicators to RRC of the UE.These OOS indicators are reported at the UE-SCG 704 functionalitythrough the use of an incrementing OOS counter. Further, in someembodiments, once the OOS counter has reached a certain value, a T310timer may be started that the UE will use to determine when to report anRLF of the SCG SpCell to the MN. Accordingly, the UE of the flow diagram700 may watch for either of the incrementing of the OOS counter and/orthe running of the T310 timer (as a “handover condition 718”) in orderto trigger balance of the flow diagram 700.

Once the handover condition 718 has been identified at the UE, the UEmay in response send SCG measurement reports. One or more of these maybe as the SCG measurement report 720, which is sent (via RRC) from theUE-SCG 704 to the source SN 708 on SRB3, in the manner describedpreviously. However, the sending of the SCG measurement report 720 tothe source SN 708 may fail as a result of the SCG SpCell degradation.The SCG measurement report is also provided 722 to the UE-MCG 702, whichthen sends it (via E-UTRA-RRC) to the MN 706 on SRB1 as part of aULInformationTransferMRDC message 724. The ULInformationTransferMRDCmessage 724 may be a message that indicates to the receiving MN that thecontents of such message should be forwarded to the current SN. Notethat while not illustrated, the UE-MCG 702 may continue to (re)send theULInformationTransferMRDC message 724 (perhaps with an updated SCGmeasurement report) on SRB1 until handover of the UE to the target SN710 is ultimately achieved (or SCG SpCell conditions improve).

As illustrated, once the MN 706 receives the ULInformationTransferMRDCmessage 724, the SCG measurement report 726 is forwarded to the sourceSN 708. Thus, in embodiments according to FIG. 7, even if the SCGmeasurement report 720 fails, it is likely that the information stillreaches the source SN 708 in any event, due to fact that it was (also)sent by the UE-MCG 702 to the MN 706 and from there forwarded to thesource SN 708.

As illustrated in FIG. 7, the source SN 708, having received the SCGmeasurement report 726 from the UE-MCG 702, is accordingly capable,based on the contents of the source SN 708, of recognizing the relevantaspects of the condition of the degrading SCG SpCell. For example, theSCG measurement report 726 may indicate that a power level of the SCGSpCell at the UE is poor or otherwise not suitable. The SCG measurementreport 726 may also aid in the identification of a suitable neighborcell on the target SN 710 (e.g., according to a power of the neighborcell as reported in the SCG measurement report 726). The source SN 708accordingly determines that a handover to the identified neighbor cellof the target SN 710 is appropriate, and sends a handover request 728 tothe target SN 710 to initiate this process.

The target SN 710 replies to the source SN 708 with a handover command730, which is forwarded 732 to the MN 706. The MN 706 then sends an RRCConnection Reconfiguration message 734 containing a SpCell Handovermessage from the handover command 730/732 informing the UE-MCG 702 ofthe handover to the identified neighbor cell on the target SN 710. Acorresponding handover command 736 containing the SpCell Handovermessage is generated by the UE-MCG 702 functionality and sent to theUE-SCG 704. The UE-SCG 704 then performs the SpCell change 738 to theneighbor cell.

To perform the SpCell change 738, the UE-SCG 704 hands over to neighborcell of the target SN 710, as instructed by the handover command 736.After handover, this neighbor cell acts as the SpCell for the UE-SCG704. This SpCell has an associated SCG and SN (the target SN 710).

It is contemplated that the SN performing a handover determines that theneighbor cell to handover to is a cell of a different NR node.Accordingly, in this sense of FIG. 7, it may be that the source SN 708and the target SN 710 are different NR nodes. It is contemplated that inthese cases, the new SpCell will accordingly be part of a new SCG havingzero or more additional cells other than those of the SCG associatedwith the prior SpCell, as provided by the new NR node.

It is further contemplated that the target SN may be the same NR node asthe current SN. For example, in the case where a SN performing ahandover determines that the neighbor cell to handover to is anothercell of the same NR node, this is allowed. Accordingly, in the sense ofFIG. 7, it may be that the source SN 708 and the target SN 710 are thesame NR node. It is contemplated that in these cases, the new SpCell forthe UE may accordingly be associated with an SCG constituted of a same,a different, or a partially different set of zero or more additionalcells as compared to the SCG associated with the prior SpCell. In thecase of, for example, the source SN 708 and the target SN 710 being thesame NR node, the handover request 728 and the handover command 730 asillustrated may not be passed (or may be handled only internally to thatsame NR node).

After completing the SpCell change 738, the UE-SCG 704 functionalityprovides the handover complete message 740 to the UE-MCG 702functionality of the UE. The UE-MCG 702 then sends the RRC ConnectionReconfiguration Complete message 742 containing the handover completemessage 740 to the MN 706, which then forwards 744 the handover completemessage 740 to the target SN 710 to inform/confirm to the target SN 710that the UE has completed the instructed handover. At this stage, theUE-SCG 704 also stops 746 any measurement reports on the SRB1 associatedwith the handover condition 718 (which may have been intentionallyrepeated until handover was performed by the network, as describedabove).

Compared to embodiments found in, for example, FIG. 3, a system forNR-DC as in FIG. 7 that detects the handover condition 718 and reacts asdescribed may be more responsive to the degrading of the SCG SpCell ofthe source SN 708. Accordingly, the risk of substantial impediment ofservices to the UE that are being provided by the source SN 708 (and,after handover, perhaps the target SN 710) is reduced.

FIG. 8 illustrates a flow diagram 800 of a system using EN-DC that isconfigured to send SCG measurement reports to both an MN and an SN inresponse to a handover condition associated with the SN and when SRB3 isconfigured between a UE and the SN, according to an embodiment. In FIG.8, the UE functionality has been split into the functionalities of theUE-MCG 802, which illustrates the functions of the UE as they relate tothe MN/MCG, and the UE-SCG 804, which illustrates the functions of the(same) UE as they relate to the one or more SNs/SCGs. The flow diagram800 also includes an MN 806 and a source SN 808 which at the beginningof the flow diagram 800 are in communication with the UE according to anEN-DC mode as previously described (with the MN 806 being an LTE nodeand the source SN 808 being an NR node). By the end of the flow diagram800, the source SN 808 will handover to the target SN 810. Note that insome cases, it is anticipated that the source SN 808 and the target SN810 may be the same NR nodes, while in other cases the source SN 808 andthe target SN 810 may be different NR nodes.

The flow diagram 800 illustrates the configuration 812 of an SRB1 and anSRB2 at the UE-MCG 802. The flow diagram 800 further illustrates theconfiguration 814 of an SRB3 at the UE-SCG 804. Because of the priorconfiguration 814 of SRB3, it may be that the UE is to make the SCGmeasurement reports 816 on SRB3, between the UE-SCG 804 and the sourceSN 808.

The flow diagram 800 then illustrates that the SpCell of the SCG startsdegrading, which causes the handover condition 818. Examples of ahandover conditions as used in the flow diagram 800 may include that anout-of-sync (OOS) counter begins incrementing, or that a T310 timer isrunning at the UE. For example, as the SpCell of the SCG degrades, theUE may begin to fall out of synchronization with it. This is detected bylower layers at the UE, which send OOS indicators to RRC of the UE.These OOS indicators are reported at the UE-SCG 804 functionalitythrough the use of an incrementing OOS counter. Further, in someembodiments, once the OOS counter has reached a certain value, a T310timer may be started that the UE will use to determine when to report anRLF of the SCG SpCell to the MN. Accordingly, the UE of the flow diagram800 may watch for either of the incrementing of the OOS counter and/orthe running of the T310 timer (as a “handover condition 818”) in orderto trigger balance of the flow diagram 800.

Once the handover condition 818 has been identified at the UE, the UEmay in response send SCG measurement reports. One or more of these maybe as the SCG measurement report 820, which is sent from the UE-SCG 804to the source SN 808 on SRB3, in the manner described previously.However, the sending of the SCG measurement report 820 to the source SN808 may fail as a result of the SCG SpCell degradation. The SCGmeasurement report is also provided 822 to the UE-MCG 802, which thensends it (via E-UTRA-RRC) to the MN 806 on SRB1 as part of aULInformationTransferMRDC message 824. The ULInformationTransferMRDCmessage 824 may be a message that indicates to the receiving MN that thecontents of such message should be forwarded to the current SN. Notethat while not illustrated, the UE-MCG 802 may continue to (re)send theULInformationTransferMRDC message 824 (perhaps with an updated SCGmeasurement report) on SRB1 until handover of the UE to the target SN810 is ultimately achieved (or SCG SpCell conditions improve).

As illustrated, once the MN 806 receives the ULInformationTransferMRDCmessage 824, the SCG measurement report 826 is forwarded to the sourceSN 808. Thus, in embodiments according to FIG. 8, even if the SCGmeasurement report 820 fails, it is likely that the information stillreaches the source SN 808 in any event, due to fact that it was (also)sent by the UE-MCG 802 to the MN 806 and from there forwarded to thesource SN 808.

As illustrated in FIG. 8, the source SN 808, having received the SCGmeasurement report 826 from the UE-MCG 802, is accordingly capable,based on the contents of the source SN 808, of recognizing the relevantaspects of the condition of the degrading SCG SpCell. For example, theSCG measurement report 826 may indicate that a power level of the SCGSpCell at the UE is poor or otherwise not suitable. The SCG measurementreport 826 may also aid in the identification of a suitable neighborcell on the target SN 810 (e.g., according to a power of the neighborcell as reported in the SCG measurement report 826). The source SN 808accordingly determines that a handover to the identified neighbor cellof the target SN 810 is appropriate, and sends a handover request 8281to the target SN 810 to initiate this process.

The target SN 810 replies to the source SN 808 with a handover command830, which is forwarded 832 to the MN 806. The MN 806 then sends an RRCConnection Reconfiguration message 834 containing a SpCell Handovermessage from the handover command 830/832 informing the UE-MCG 802 ofthe handover to the identified neighbor cell on the target SN 810. Acorresponding handover command 836 containing the SpCell Handovermessage is generated by the UE-MCG 802 functionality and sent to theUE-SCG 804. The UE-SCG 804 then performs the SpCell change 838 to theneighbor cell.

To perform the SpCell change 838, the UE-SCG 804 hands over to neighborcell of the target SN 810, as instructed by the handover command 836.After handover, this neighbor cell acts as the SpCell for the UE-SCG804. This SpCell has an associated SCG and SN (the target SN 810).

It is contemplated that the SN performing a handover determines that theneighbor cell to handover to is a cell of a different NR node.Accordingly, in this sense of FIG. 8, it may be that the source SN 808and the target SN 810 are different NR nodes. It is contemplated that inthese cases, the new SpCell will accordingly be part of a new SCG havingzero or more additional cells other than those of the SCG associatedwith the prior SpCell, as provided by the new NR node.

It is further contemplated that the target SN may be the same NR node asthe current SN. For example, in the case where a SN performing ahandover determines that the neighbor cell to handover to is anothercell of the same NR node, this is allowed. Accordingly, in the sense ofFIG. 8, it may be that the source SN 808 and the target SN 810 are thesame NR node. It is contemplated that in these cases, the new SpCell forthe UE may accordingly be associated with an SCG constituted of a same,a different, or a partially different set of zero or more additionalcells as compared to the SCG associated with the prior SpCell. In thecase of, for example, the source SN 808 and the target SN 810 being thesame NR node, the handover request 828 and the handover command 830 asillustrated may not be passed (or may be handled only internally to thatsame NR node).

After completing the SpCell change 838, the UE-SCG 804 functionalityprovides the handover complete message 840 to the UE-MCG 802functionality of the UE. The UE-MCG 802 then sends the RRC ConnectionReconfiguration Complete message 842 containing the handover completemessage 840 to the MN 806, which forwards the forwards 844 the handovercomplete message 840 to the target SN 810 to inform/confirm to thetarget SN 810 that the UE has completed the instructed handover. At thisstage, the UE-SCG 804 also stops 846 any measurement reports on the SRB1associated with the handover condition 818 (which may have beenintentionally repeated until handover was performed by the network, asdescribed above).

Compared to embodiments found in, for example, FIG. 4, a system forEN-DC as in FIG. 8 that detects the handover condition 818 and reacts asdescribed may be more responsive to the degrading of the SCCG SpCell ofthe source SN 808. Accordingly, the risk of substantial impediment ofservices to the UE that are being provided by the source SN 808 (and,after handover, perhaps the target SN 810) is reduced.

FIG. 9 illustrates a flow diagram 900 of a system using NR-DC that isconfigured to send SCG measurement reports to both an MN and an SN inresponse to a handover condition associated with the SN and when SRB3 isconfigured between a UE and the SN, according to an embodiment. In FIG.9, the UE functionality has been split into the functionalities of theUE-MCG 902, which illustrates the functions of the UE as they relate tothe MN/MCG, and the UE-SCG 904, which illustrates the functions of the(same) UE as they relate to the one or more SNs/SCGs. The flow diagram900 also includes an MN 906 and a source SN 908 which at the beginningof the flow diagram 900 are in communication with the UE according to anNR-DC mode as previously described (with both the MN 906 and the sourceSN 908 being NR nodes). By the end of the flow diagram 900, the sourceSN 908 will handover to the target SN 910. Note that in some cases, itis anticipated that the source SN 908 and the target SN 910 may be thesame NR node, while in other cases the source SN 908 and the target SN910 may be different NR nodes.

The flow diagram 900 illustrates the configuration 912 of an SRB1 and anSRB2 at the UE-MCG 902. The flow diagram 900 further illustrates theconfiguration 914 of an SRB3 at the UE-SCG 904. Because of the priorconfiguration 914 of SRB3, it may be that the UE is to make the SCGmeasurement reports 916 on SRB3, between the UE-SCG 904 and the sourceSN 908.

The flow diagram 900 then illustrates the handover condition 718, whichis an identification by the UE that Event A3 criteria has been satisfiedas between the SCG SpCell of the source SN 908 and a neighbor cell. Forexample, the UE may identify that a neighbor cell on the target SN 910is better (e.g., has a higher power measured at the UE) than the SCGSpCell on the source SN 908 by a threshold amount.

Once the handover condition 918 has been identified at the UE, the UEmay send SCG measurement reports (Event A3). One or more of these may beas the SCG measurement report (Event A3) 920, which is sent from theUE-SCG 904 to the source SN 908 on SRB3, in the manner describedpreviously. However, the sending of the SCG measurement report (EventA3) 920 to the source SN 908 may fail as a result of any degradation onthe current SCG SpCell (e.g., in the case that degradation of thecurrent SCG SpCell was a cause of the A3 condition between the SCGSpCell and the neighbor cell). The SCG measurement report is alsoprovided 922 to the UE-MCG 902, which then sends it (via RRC) to the MN906 on SRB1 as part of a ULInformationTransferMRDC message 924. TheULInformationTransferMRDC message 924 may be a message that indicates tothe receiving MN that the contents of such message should be forwardedto the current SN. Note that while not illustrated, the UE-MCG 902 (viaRRC) may continue to (re)send the ULInformationTransferMRDC message 924(perhaps with an updated SCG measurement report (Event A3)) on SRB1until handover of the UE to the target SN 910 is ultimately achieved (orSCG SpCell conditions improve).

As illustrated, once the MN 906 receives the ULInformationTransferMRDCmessage 924, the SCG measurement report (Event A3) 926 is forwarded tothe source SN 908. Thus, in embodiments according to FIG. 9, even if theSCG measurement report (Event A3) 920 fails, it is likely that theinformation still reaches the source SN 908 in any event, due to factthat it was (also) sent by the UE-MCG 902 to the MN 906 and from thereforwarded to the source SN 908.

As illustrated in FIG. 9, the source SN 908, having received the SCGmeasurement report (Event A3) 926 from the UE-MCG 902, is therebyinformed of the existence of the A3 condition and the identity of theneighbor cell on the target SN 910. The source SN 908 accordinglydetermines that a handover to the identified neighbor cell of the targetSN 910 is appropriate, and sends a handover request 928 to the target SN910 to initiate this process.

The target SN 910 replies to the source SN 908 with a handover command930, which is forwarded 932 to the MN 906. The MN 906 then sends an RRCConnection Reconfiguration message 934 containing a SpCell Handovermessage from the handover command 930/932 informing the UE-MCG 902 ofthe handover to the identified neighbor cell of the target SN 910. Acorresponding handover command 936 containing the SpCell Handovermessage is generated by the UE-MCG 902 functionality and sent to theUE-SCG 904. The UE-SCG 904 then performs the SpCell change 938 to theneighbor cell.

To perform the SpCell change 938, the UE-SCG 904 hands over to theneighbor cell of the target SN 910, as instructed by the handovercommand 936. After handover, this neighbor cell acts as the SpCell forthe UE-SCG 904. This SpCell has an associated SCG and SN (the target SN910).

It is contemplated that the SN performing a handover determines that theneighbor cell to handover to is a cell of a different NR node.Accordingly, in this sense of FIG. 9, it may be that the source SN 908and the target SN 910 are different NR nodes. It is contemplated that inthese cases, the new SpCell will accordingly be part of a new SCG havingzero or more additional cells other than those of the SCG associatedwith the prior SpCell, as provided by the new NR node.

It is further contemplated that the target SN may be the same NR node asthe current SN. For example, in the case where a SN performing ahandover determines that the neighbor cell to handover to is anothercell of the same NR node, this is allowed. Accordingly, in the sense ofFIG. 9, it may be that the source SN 908 and the target SN 910 are thesame NR node. It is contemplated that in these cases, the new SpCell forthe UE may accordingly be associated with an SCG constituted of a same,a different, or a partially different set of zero or more additionalcells as compared to the SCG associated with the prior SpCell. In thecase of, for example, the source SN 908 and the target SN 910 being thesame NR node, the handover request 928 and the handover command 930 asillustrated may not be passed (or may be handled only internally to thatsame NR node).

After completing the SpCell change 1038, the UE-SCG 1004 functionalityprovides the handover complete message 1040 to the UE-MCG 1002functionality of the UE. The UE-MCG 1002 then sends the RRC ConnectionReconfiguration Complete message 1042 containing the handover completemessage 1040 to the MN 1006, which forwards 1044 the handover completemessage 1040 to the target SN 1010 to inform/confirm to the target SN1010 that the UE has completed the instructed handover. At this stage,the UE-SCG 1004 also stops 1046 any measurement reports on the SRB1associated with the handover condition 1018 (which may have beenintentionally repeated until handover was performed by the network, asdescribed above).

Compared to embodiments found in, for example, FIG. 6, a system forEN-DC as in FIG. 10 that detects the handover condition 1018 and reactsas described may be more responsive to the potential degrading of theSCG SpCell of the source SN 1008 that may be a cause of the A3condition. Accordingly, the risk of substantial impediment of servicesto the UE that are being provided by the source SN 1008 (and, afterhandover, perhaps the target SN 1010) is reduced.

FIG. 10 illustrates a flow diagram 1000 of a system using EN-DC that isconfigured to send SCG measurement reports to both an MN and an SN inresponse to a handover condition associated with the SN and when SRB3 isconfigured between a UE and the SN, according to an embodiment. In FIG.10, the UE functionality has been split into the functionalities of theUE-MCG 1002, which illustrates the functions of the UE as they relate tothe MN/MCG, and the UE-SCG 1004, which illustrates the functions of the(same) UE as they relate to the one or more SNs/SCGs. The flow diagram1000 also includes an MN 1006 and a source SN 1008 which at thebeginning of the flow diagram 1000 are in communication with the UEaccording to an EN-DC mode as previously described (with the MN 1006being an LTE node and the source SN 1008 being an NR node). By the endof the flow diagram 1000, the source SN 1008 will handover to the targetSN 1010. Note that in some cases, it is anticipated that the source SN1008 and the target SN 1010 may be the same NR node, while in othercases the source SN 1008 and the target SN 1010 may be different NRnodes.

The flow diagram 1000 illustrates the configuration 1012 of an SRB1 andan SRB2 at the UE-MCG 1002. The flow diagram 1000 further illustratesthe configuration 1014 of an SRB3 at the UE-SCG 1004. Because of theprior configuration 1014 of SRB3, it may be that the UE is to make theSCG measurement reports 1016 on SRB3, between the UE-SCG 1004 and thesource SN 1008.

The flow diagram 1000 then illustrates the handover condition 1018,which is an identification by the UE that Event A3 criteria has beensatisfied as between the SCG SpCell of the source SN 1008 and a neighborcell. For example, the UE may identify that a neighbor cell on thetarget SN 1010 is better (e.g., has a higher power measured at the UE)than the SCG SpCell on the source SN 1008 by a threshold amount.

Once the handover condition 1018 has been identified at the UE, the UEmay send SCG measurement reports (Event A3). One or more of these may beas the SCG measurement report (Event A3) 1020, which is sent from theUE-SCG 1004 to the source SN 1008 on SRB3, in the manner describedpreviously. However, the sending of the SCG measurement report (EventA3) 1020 to the source SN 1008 may fail as a result of any degradationon the current SCG SpCell (e.g., in the case that degradation of thecurrent SCG SpCell was a cause of the A3 condition between the SCGSpCell and the neighbor cell). The SCG measurement report is alsoprovided 1022 to the UE-MCG 1002, which then sends it (via RRC) to theMN 1006 on SRB1 as part of a ULInformationTransferMRDC message 1024. TheULInformationTransferMRDC message 1024 may be a message that indicatesto the receiving MN that the contents of such message should beforwarded to the current SN. Note that while not illustrated, the UE-MCG1002 (via RRC) may continue to (re)send the ULInformationTransferMRDCmessage 1024 (perhaps with an updated SCG measurement report (Event A3))on SRB1 until handover of the UE to the target SN 1010 is ultimatelyachieved (or SCG SpCell conditions improve).

As illustrated, once the MN 1006 receives the ULInformationTransferMRDCmessage 1024, the SCG measurement report (Event A3) 1026 is forwarded tothe source SN 1008. Thus, in embodiments according to FIG. 10, even ifthe SCG measurement report (Event A3) 1020 fails, it is likely that theinformation still reaches the source SN 1008 in any event, due to factthat it was (also) sent by the UE-MCG 1002 to the MN 1006 and from thereforwarded to the source SN 1008.

As illustrated in FIG. 10, the source SN 1008, having received the SCGmeasurement report (Event A3) 1026 from the UE-MCG 1002, is therebyinformed of the existence of the A3 condition and the identity of theneighbor cell on the target SN 1010. The source SN 1008 accordinglydetermines that a handover to the identified neighbor cell of the targetSN 1010 is appropriate, and sends a handover request 1028 to the targetSN 1010 to initiate this process.

The target SN 1010 replies to the source SN 1008 with a handover command1030, which is forwarded 1032 to the MN 1006. The MN 1006 then sends anRRC Connection Reconfiguration message 1034 containing a SpCell Handovermessage from the handover command 1030/1032 informing the UE-MCG 1002 ofthe handover to the identified neighbor cell of the target SN 1010. Acorresponding handover command 1036 containing the SpCell Handovermessage is generated by the UE-MCG 1002 functionality and sent to theUE-SCG 1004. The UE-SCG 1004 then performs the SpCell change 1038 to theneighbor cell.

To perform the SpCell change 1038, the UE-SCG 1004 hands over to theneighbor cell of the target SN 1010, as instructed by the handovercommand 1036. After handover, this neighbor cell acts as the SpCell forthe UE-SCG 1004. This SpCell has an associated SCG and SN (the target SN1010).

It is contemplated that the SN performing a handover determines that theneighbor cell to handover to is a cell of a different NR node.Accordingly, in this sense of FIG. 10, it may be that the source SN 1008and the target SN 1010 are different NR nodes. It is contemplated thatin these cases, the new SpCell will accordingly be part of a new SCGhaving zero or more additional cells other than those of the SCGassociated with the prior SpCell, as provided by the new NR node.

It is further contemplated that the target SN may be the same NR node asthe current SN. For example, in the case where a SN performing ahandover determines that the neighbor cell to handover to is anothercell of the same NR node, this is allowed. Accordingly, in the sense ofFIG. 10, it may be that the source SN 1008 and the target SN 1010 arethe same NR node. It is contemplated that in these cases, the new SpCellfor the UE may accordingly be associated with an SCG constituted of asame, a different, or a partially different set of zero or moreadditional cells as compared to the SCG associated with the priorSpCell. In the case of, for example, the source SN 1008 and the targetSN 1010 being the same NR node, the handover request 1028 and thehandover command 1030 as illustrated may not be passed (or may behandled only internally to that same NR node).

After completing the SpCell change 938, the UE-SCG 904 functionalityprovides the handover complete message 940 to the UE-MCG 902functionality of the UE. The UE-MCG 902 then sends the RRC ConnectionReconfiguration Complete message 942 containing the handover completemessage 940 to the MN 906, which forwards 944 the handover completemessage 940 to the target SN 910 to inform/confirm to the target SN 910that the UE has completed the instructed handover. At this stage, theUE-SCG 904 also stops 946 any measurement reports on the SRB1 associatedwith the handover condition 918 (which may have been intentionallyrepeated until handover was performed by the network, as describedabove).

Compared to embodiments found in, for example, FIG. 5, a system forNR-DC as in FIG. 9 that detects the handover condition 918 and reacts asdescribed may be more responsive to the potential degrading of the SCGSpCell of the source SN 908 that may be a cause of the A3 condition.Accordingly, the risk of substantial impediment of services to the UEthat are being provided by the source SN 908 (and, after handover,perhaps the target SN 910) is reduced.

FIG. 11 illustrates a method 1100 of a UE operating in an MR-DC modewith an MN and an SN, according to an embodiment. The method 1100includes identifying 1102 that a handover condition for an SpCell of anSCG of the SN is met.

The method 1100 further includes sending 1104 an SCG measurement reportto the SN on a first SRB. This may occur in response to the identifying1102 that the handover condition of the SpCell of the SCG of the SN ismet.

The method 1100 further includes sending 1106 the SCG measurement reportto the MN on a second SRB. This may occur in response to the identifying1102 that the handover condition of the SpCell of the SCG of the SN ismet.

In some embodiments of the method 1100, the identifying 1102 that thehandover condition for the SpCell is met comprises identifying that aneighbor cell of a target node is better than the SpCell by a thresholdamount.

In some embodiments of the method 1100, the identifying 1102 that thehandover condition for the SpCell is met comprises identifying that oneor more OOS indications have been received from a lower layer.

In some embodiments of the method 1100, the identifying 1102 that thehandover condition for the SpCell is met comprises identifying that aT310 timer is running at the UE.

In some embodiments of the method 1100, the SCG measurement report thatis sent to the MN on the second SRB is sent in aULInformationTransferMRDC message.

In some embodiments of the method 1100, the first SRB is an SRB3 and thesecond SRB is an SRB1.

In some embodiments of the method 1100, the SCG of the SN comprises aplurality of cells including the SpCell.

In some embodiments of the method 1100, the MR-DC mode is an NR-DC mode.

In some embodiments of the method 1100, the MR-DC mode is an EN-DC mode.

Embodiments contemplated herein include an apparatus comprising means toperform one or more elements of the method 1200. This apparatus may be,for example, an apparatus of a UE 1300 as described below.

Embodiments contemplated herein include one or more non-transitorycomputer-readable media comprising instructions to cause an electronicdevice, upon execution of the instructions by one or more processors ofthe electronic device, to perform one or more elements of the method1100. This non-transitory computer-readable media may be, for example,the memory 1306 of the UE 1300 described below, and/or the peripheraldevices 1504, the memory/storage devices 1514, and/or the databases 1520of the components 1500 as described below.

Embodiments contemplated herein include an apparatus comprising logic,modules, or circuitry to perform one or more elements of the method1100. This apparatus may be, for example, an apparatus of a UE 1300 asdescribed below.

Embodiments contemplated herein include an apparatus comprising: one ormore processors and one or more computer-readable media comprisinginstructions that, when executed by the one or more processors, causethe one or more processors to perform one or more elements of the method1100. This apparatus may be, for example, an apparatus of a UE 1300 asdescribed below.

Embodiments contemplated herein include a signal as described in orrelated to one or more elements of the method 1100.

Embodiments contemplated herein include a computer program comprisinginstructions, wherein execution of the program by a processing elementis to cause the processing element to carry out one or more elements ofthe method 1100. These instructions may be, for example, theinstructions 1512 of the components 1500 as described below.

FIG. 12 illustrates a method 1200 of an SN operable with a UE using anMR-DC mode with an MN and the SN, according to an embodiment. The method1200 includes establishing 1202, with the UE, an SRB.

The method 1200 further includes receiving 1204, from an MN, an SCGmeasurement report.

The method 1200 further includes determining 1206, based on contents ofthe SCG measurement report, to perform a handover from a SpCell of theSN to a neighbor cell of a target node.

The method 1200 further includes sending 1208, to the target node, ahandover request. This may occur in the case where the SN is a differentNR node than the target node, but may not occur in the case where the SNis the same NR node as the target node.

In some embodiments of the method 1200, the determining 1206, based onthe contents of the SCG measurement report, to perform the handovercomprises comparing a difference between a power level of the SpCell ofthe SN from the SCG measurement report and a power level of the neighborcell of the target node from the SCG measurement report to a thresholdamount.

In some embodiments of the method 1200, the SRB is an SRB3.

In some embodiments of the method 1200, the MR-DC is an NR-DC mode.

In some embodiments of the method 1200, the MR-DC mode is an EN-DC mode.

In some embodiments of the method 1200, the target node is the SN.

Embodiments contemplated herein include an apparatus comprising means toperform one or more elements of the method 1200. This apparatus may be,for example, an apparatus of a network node 1400 as described below.

Embodiments contemplated herein include one or more non-transitorycomputer-readable media comprising instructions to cause an electronicdevice, upon execution of the instructions by one or more processors ofthe electronic device, to perform one or more elements of the method1200. This non-transitory computer-readable media may be, for example,the memory 1406 of the network node 1400 described below, and/or theperipheral devices 1504, the memory/storage devices 1514, and/or thedatabases 1520 of the components 1500 as described below.

Embodiments contemplated herein include an apparatus comprising logic,modules, or circuitry to perform one or more elements of the method1200. This apparatus may be, for example, an apparatus of a network node1400 as described below.

Embodiments contemplated herein include an apparatus comprising: one ormore processors and one or more computer-readable media comprisinginstructions that, when executed by the one or more processors, causethe one or more processors to perform one or more elements of the method1200. This apparatus may be, for example, an apparatus of a network node1400 as described below.

Embodiments contemplated herein include a signal as described in orrelated to one or more elements of the method 1200.

Embodiments contemplated herein include a computer program comprisinginstructions, wherein execution of the program by a processing elementis to cause the processing element to carry out one or more elements ofthe method 1200. These instructions may be, for example, theinstructions 1512 of the components 1500 as described below.

FIG. 13 is a block diagram of an example UE 1300 configurable accordingto various embodiments of the present disclosure, including by executionof instructions on a computer-readable medium that correspond to any ofthe example methods and/or procedures described herein. The UE 1300comprises one or more processor 1302, transceiver 1304, memory 1306,user interface 1308, and control interface 1310.

The one or more processor 1302 may include, for example, an applicationprocessor, an audio digital signal processor, a central processing unit,and/or one or more baseband processors. Each of the one or moreprocessor 1302 may include internal memory and/or may includeinterface(s) to communication with external memory (including the memory1306). The internal or external memory can store software code,programs, and/or instructions for execution by the one or more processor1302 to configure and/or facilitate the UE 1300 to perform variousoperations, including operations described herein. For example,execution of the instructions can configure the UE 1300 to communicateusing one or more wired or wireless communication protocols, includingone or more wireless communication protocols standardized by 3GPP suchas those commonly known as 5G/NR, LTE, LTE-A, UMTS, HSPA, GSM, GPRS,EDGE, etc., or any other current or future protocols that can beutilized in conjunction with the one or more transceiver 1304, userinterface 1308, and/or control interface 1310. As another example, theone or more processor 1302 may execute program code stored in the memory1306 or other memory that corresponds to MAC, RLC, PDCP, and RRC layerprotocols standardized by 3GPP (e.g., for NR and/or LTE). As a furtherexample, the processor 1302 may execute program code stored in thememory 1306 or other memory that, together with the one or moretransceiver 1304, implements corresponding PHY layer protocols, such asOrthogonal Frequency Division Multiplexing (OFDM), Orthogonal FrequencyDivision Multiple Access (OFDMA), and Single-Carrier Frequency DivisionMultiple Access (SC-FDMA).

The memory 1306 may comprise memory area for the one or more processor1302 to store variables used in protocols, configuration, control, andother functions of the UE 1300, including operations corresponding to,or comprising, any of the example methods and/or procedures describedherein. Moreover, the memory 1306 may comprise non-volatile memory(e.g., flash memory), volatile memory (e.g., static or dynamic RAM), ora combination thereof. Furthermore, the memory 1306 may interface with amemory slot by which removable memory cards in one or more formats(e.g., SD Card, Memory Stick, Compact Flash, etc.) can be inserted andremoved.

The one or more transceiver 1304 may include radio-frequency transmitterand/or receiver circuitry that facilitates the UE 1300 to communicatewith other equipment supporting like wireless communication standardsand/or protocols. For example, the one or more transceiver 1304 mayinclude switches, mixer circuitry, amplifier circuitry, filtercircuitry, and synthesizer circuitry. Such RF circuitry may include areceive signal path with circuitry to down-convert RF signals receivedfrom a front-end module (FEM) and provide baseband signals to a basebandprocessor of the one or more processor 1302. The RF circuitry may alsoinclude a transmit signal path which may include circuitry to up-convertbaseband signals provided by a baseband processor and provide RF outputsignals to the FEM for transmission. The FEM may include a receivesignal path that may include circuitry configured to operate on RFsignals received from one or more antennas, amplify the received signalsand provide the amplified versions of the received signals to the RFcircuitry for further processing. The FEM may also include a transmitsignal path that may include circuitry configured to amplify signals fortransmission provided by the RF circuitry for transmission by one ormore antennas. In various embodiments, the amplification through thetransmit or receive signal paths may be done solely in the RF circuitry,solely in the FEM, or in both the RF circuitry and the FEM circuitry. Insome embodiments, the FEM circuitry may include a TX/RX switch to switchbetween transmit mode and receive mode operation.

In some exemplary embodiments, the one or more transceiver 1304 includesa transmitter and a receiver that enable the UE 1300 to communicate withvarious 5G/NR networks according to various protocols and/or methodsproposed for standardization by 3 GPP and/or other standards bodies. Forexample, such functionality can operate cooperatively with the one ormore processor 1302 to implement a PHY layer based on OFDM, OFDMA,and/or SC-FDMA technologies, such as described herein with respect toother figures.

The user interface 1308 may take various forms depending on particularembodiments, or can be absent from the UE 1300. In some embodiments, theuser interface 1308 includes a microphone, a loudspeaker, slidablebuttons, depressible buttons, a display, a touchscreen display, amechanical or virtual keypad, a mechanical or virtual keyboard, and/orany other user-interface features commonly found on mobile phones. Inother embodiments, the UE 1300 may comprise a tablet computing deviceincluding a larger touchscreen display. In such embodiments, one or moreof the mechanical features of the user interface 1308 may be replaced bycomparable or functionally equivalent virtual user interface features(e.g., virtual keypad, virtual buttons, etc.) implemented using thetouchscreen display, as familiar to persons of ordinary skill in theart. In other embodiments, the UE 1300 may be a digital computingdevice, such as a laptop computer, desktop computer, workstation, etc.that comprises a mechanical keyboard that can be integrated, detached,or detachable depending on the particular exemplary embodiment. Such adigital computing device can also comprise a touch screen display. Manyexample embodiments of the UE 1300 having a touch screen display arecapable of receiving user inputs, such as inputs related to exemplarymethods and/or procedures described herein or otherwise known to personsof ordinary skill in the art.

In some exemplary embodiments of the present disclosure, the UE 1300 mayinclude an orientation sensor, which can be used in various ways byfeatures and functions of the UE 1300. For example, the UE 1300 can useoutputs of the orientation sensor to determine when a user has changedthe physical orientation of the UE 1300's touch screen display. Anindication signal from the orientation sensor can be available to anyapplication program executing on the UE 1300, such that an applicationprogram can change the orientation of a screen display (e.g., fromportrait to landscape) automatically when the indication signalindicates an approximate 90-degree change in physical orientation of thedevice. In this manner, the application program can maintain the screendisplay in a manner that is readable by the user, regardless of thephysical orientation of the device. In addition, the output of theorientation sensor can be used in conjunction with various exemplaryembodiments of the present disclosure.

The control interface 1310 may take various forms depending onparticular embodiments. For example, the control interface 1310 mayinclude an RS-232 interface, an RS-485 interface, a USB interface, anHDMI interface, a Bluetooth interface, an IEEE (“Firewire”) interface,an I²C interface, a PCMCIA interface, or the like. In some exemplaryembodiments of the present disclosure, control interface 1260 cancomprise an IEEE 802.3 Ethernet interface such as described above. Insome embodiments of the present disclosure, the control interface 1310may include analog interface circuitry including, for example, one ormore digital-to-analog (D/A) and/or analog-to-digital (A/D) converters.

Persons of ordinary skill in the art can recognize the above list offeatures, interfaces, and radio-frequency communication standards ismerely exemplary, and not limiting to the scope of the presentdisclosure. In other words, the UE 1300 may include more functionalitythan is shown in FIG. 13 including, for example, a video and/orstill-image camera, microphone, media player and/or recorder, etc.Moreover, the one or more transceiver 1304 may include circuitry forcommunication using additional radio-frequency communication standardsincluding Bluetooth, GPS, and/or others. Moreover, the one or moreprocessor 1302 may execute software code stored in the memory 1306 tocontrol such additional functionality. For example, directional velocityand/or position estimates output from a GPS receiver can be available toany application program executing on the UE 1300, including variousexemplary methods and/or computer-readable media according to variousexemplary embodiments of the present disclosure.

FIG. 14 is a block diagram of an example network node 1400 configurableaccording to various embodiments of the present disclosure, including byexecution of instructions on a computer-readable medium that correspondto any of the example methods and/or procedures described herein.

The network node 1400 includes a one or more processor 1402, a radionetwork interface 1404, a memory 1406, a core network interface 1408,and other interfaces 1410. The network node 1400 may comprise, forexample, a base station, eNB, gNB, access node, or component thereof.The network node 1400 may comprise an LTE node or an NR node, as thoseterms are used in this disclosure.

The one or more processor 1402 may include any type of processor orprocessing circuitry and may be configured to perform any of the methodsor procedures disclosed herein. The memory 1406 may store software code,programs, and/or instructions executed by the one or more processor 1402to configure the network node 1400 to perform various operations,including operations described herein. For example, execution of suchstored instructions can configure the network node 1400 to communicatewith one or more other devices using protocols according to variousembodiments of the present disclosure, including one or more methodsand/or procedures discussed above. Furthermore, execution of such storedinstructions can also configure and/or facilitate the network node 1400to communicate with one or more other devices using other protocols orprotocol layers, such as one or more of the PHY, MAC, RLC, PDCP, and RRClayer protocols standardized by 3GPP for LTE, LTE-A, and/or NR, or anyother higher-layer protocols utilized in conjunction with the radionetwork interface 1404 and the core network interface 1408. By way ofexample and without limitation, the core network interface 1408 comprisean S1 interface and the radio network interface 1404 may comprise a Uuinterface, as standardized by 3GPP. The memory 1406 may also storevariables used in protocols, configuration, control, and other functionsof the network node 1400. As such, the memory 1406 may comprisenon-volatile memory (e.g., flash memory, hard disk, etc.), volatilememory (e.g., static or dynamic RAM), network-based (e.g., “cloud”)storage, or a combination thereof.

The radio network interface 1404 may include transmitters, receivers,signal processors, ASICs, antennas, beamforming units, and othercircuitry that enables network node 1400 to communicate with otherequipment such as, in some embodiments, a plurality of compatible userequipment (UE). In some embodiments, the network node 1400 may includevarious protocols or protocol layers, such as the PHY, MAC, RLC, PDCP,and RRC layer protocols standardized by 3GPP for LTE, LTE-A, and/or5G/NR. According to further embodiments of the present disclosure, theradio network interface 1404 may include a PHY layer based on OFDM,OFDMA, and/or SC-FDMA technologies. In some embodiments, thefunctionality of such a PHY layer can be provided cooperatively by theradio network interface 1404 and the one or more processor 1402.

The core network interface 1408 may include transmitters, receivers, andother circuitry that enables the network node 1400 to communicate withother equipment in a core network such as, in some embodiments,circuit-switched (CS) and/or packet-switched Core (PS) networks. In someembodiments, the core network interface 1408 may include the S1interface standardized by 3GPP. In some embodiments, the core networkinterface 1408 may include one or more interfaces to one or more SGWs,MMEs, SGSNs, GGSNs, and other physical devices that comprisefunctionality found in GERAN, UTRAN, E-UTRAN, and CDMA2000 core networksthat are known to persons of ordinary skill in the art. In someembodiments, these one or more interfaces may be multiplexed together ona single physical interface. In some embodiments, lower layers of thecore network interface 1408 may include one or more of asynchronoustransfer mode (ATM), Internet Protocol (IP)-over-Ethernet, SDH overoptical fiber, T1/E1/PDH over a copper wire, microwave radio, or otherwired or wireless transmission technologies known to those of ordinaryskill in the art.

The other interfaces 1410 may include transmitters, receivers, and othercircuitry that enables the network node 1400 to communicate withexternal networks, computers, databases, and the like for purposes ofoperations, administration, and maintenance of the network node 1400 orother network equipment operably connected thereto.

FIG. 15 is a block diagram illustrating components 1500, according tosome example embodiments, able to read instructions from amachine-readable or computer-readable medium (e.g., a non-transitorymachine-readable storage medium) and perform any one or more of themethodologies discussed herein. Specifically, FIG. 15 shows adiagrammatic representation of hardware resources 1502 including one ormore processors 1506 (or processor cores), one or more memory/storagedevices 1514, and one or more communication resources 1524, each ofwhich may be communicatively coupled via a bus 1516. For embodimentswhere node virtualization (e.g., NFV) is utilized, a hypervisor 1522 maybe executed to provide an execution environment for one or more networkslices/sub-slices to utilize the hardware resources 1502. The components1500 may be included in, for example, a UE or a network node asdescribed herein.

The processors 1506 (e.g., a central processing unit (CPU), a reducedinstruction set computing (RISC) processor, a complex instruction setcomputing (CISC) processor, a graphics processing unit (GPU), a digitalsignal processor (DSP) such as a baseband processor, an applicationspecific integrated circuit (ASIC), a radio-frequency integrated circuit(RFIC), another processor, or any suitable combination thereof) mayinclude, for example, a processor 1508 and a processor 1510.

The memory/storage devices 1514 may include main memory, disk storage,or any suitable combination thereof. The memory/storage devices 1514 mayinclude, but are not limited to any type of volatile or non-volatilememory such as dynamic random access memory (DRAM), static random-accessmemory (SRAM), erasable programmable read-only memory (EPROM),electrically erasable programmable read-only memory (EEPROM), Flashmemory, solid-state storage, etc.

The communication resources 1524 may include interconnection or networkinterface components or other suitable devices to communicate with oneor more peripheral devices 1504 or one or more databases 1520 via anetwork 1518. For example, the communication resources 1524 may includewired communication components (e.g., for coupling via a UniversalSerial Bus (USB)), cellular communication components, NFC components,Bluetooth® components (e.g., Bluetooth® Low Energy), Wi-Fi® components,and other communication components.

Instructions 1512 may comprise software, a program, an application, anapplet, an app, or other executable code for causing at least any of theprocessors 1506 to perform any one or more of the methodologiesdiscussed herein. The instructions 1512 may reside, completely orpartially, within at least one of the processors 1506 (e.g., within theprocessor's cache memory), the memory/storage devices 1514, or anysuitable combination thereof. Furthermore, any portion of theinstructions 1512 may be transferred to the hardware resources 1502 fromany combination of the peripheral devices 1504 or the databases 1520.Accordingly, the memory of the processors 1506, the memory/storagedevices 1514, the peripheral devices 1504, and the databases 1520 areexamples of computer-readable and machine-readable media.

For one or more embodiments, at least one of the components set forth inone or more of the preceding figures may be configured to perform one ormore operations, techniques, processes, and/or methods as set forthherein. For example, the baseband circuitry as described above inconnection with one or more of the preceding figures may be configuredto operate in accordance with one or more of the examples set forthherein. For another example, circuitry associated with a UE, basestation, network element, etc. as described above in connection with oneor more of the preceding figures may be configured to operate inaccordance with one or more of the examples set forth herein.

Any of the above described embodiments may be combined with any otherembodiment (or combination of embodiments), unless explicitly statedotherwise. The foregoing description of one or more implementationsprovides illustration and description, but is not intended to beexhaustive or to limit the scope of embodiments to the precise formdisclosed. Modifications and variations are possible in light of theabove teachings or may be acquired from practice of various embodiments.

Embodiments and implementations of the systems and methods describedherein may include various operations, which may be embodied inmachine-executable instructions to be executed by a computer system. Acomputer system may include one or more general-purpose orspecial-purpose computers (or other electronic devices). The computersystem may include hardware components that include specific logic forperforming the operations or may include a combination of hardware,software, and/or firmware.

It should be recognized that the systems described herein includedescriptions of specific embodiments. These embodiments can be combinedinto single systems, partially combined into other systems, split intomultiple systems or divided or combined in other ways. In addition, itis contemplated that parameters, attributes, aspects, etc. of oneembodiment can be used in another embodiment. The parameters,attributes, aspects, etc. are merely described in one or moreembodiments for clarity, and it is recognized that the parameters,attributes, aspects, etc. can be combined with or substituted forparameters, attributes, aspects, etc. of another embodiment unlessspecifically disclaimed herein.

It is well understood that the use of personally identifiableinformation should follow privacy policies and practices that aregenerally recognized as meeting or exceeding industry or governmentalrequirements for maintaining the privacy of users. In particular,personally identifiable information data should be managed and handledso as to minimize risks of unintentional or unauthorized access or use,and the nature of authorized use should be clearly indicated to users.

Although the foregoing has been described in some detail for purposes ofclarity, it will be apparent that certain changes and modifications maybe made without departing from the principles thereof. It should benoted that there are many alternative ways of implementing both theprocesses and apparatuses described herein. Accordingly, the presentembodiments are to be considered illustrative and not restrictive, andthe description is not to be limited to the details given herein, butmay be modified within the scope and equivalents of the appended claims.

1. A method of a secondary node (SN) operable with a user equipment (UE)using a multi-radio dual connectivity (MR-DC) mode with a master node(MN) and the SN, comprising: establishing, with the UE, a signalingradio bearer (SRB); while the SRB with the UE is established, receiving,from the MN, a secondary cell group (SCG) measurement report for the UE;and determining, based on contents of the SCG measurement report, toperform a handover from a special cell (SpCell) of the SN to a neighborcell of a target node.
 2. The method of claim 1, wherein thedetermining, based on the contents of the SCG measurement report, toperform the handover comprises comparing a difference between a powerlevel of the SpCell of the SN from the SCG measurement report and apower level of the neighbor cell of the target node from the SCGmeasurement report to a threshold amount.
 3. The method of claim 1,wherein the SRB is an SRB3.
 4. The method of claim 1, wherein the MR-DCmode is a new radio (NR)-NR dual connectivity (NR-DC) mode.
 5. Themethod of claim 1, wherein the MR-DC mode is an evolved universalterrestrial radio access (E-UTRA)-new radio (NR) dual connectivity(EN-DC) mode.
 6. The method of claim 1, wherein the target node is theSN.
 7. The method of claim 1, further comprising sending, to the targetnode, a handover request.
 8. A system for operating with a userequipment (UE) in a multi-radio dual connectivity (MR-DC) mode, thesystem comprising a master node (MN) and a secondary node (SN), wherein:the SN is in communication with the UE and the MN and comprises a firstmemory and one or more first processors configured to process an SCGmeasurement report as received from either of the UE on a firstsignaling radio bearer (SRB) and the MN; and the MN is in communicationwith the UE and the SN and comprises a second memory and one or moresecond processors configured to process the SCG measurement report asreceived from the UE on a second SRB and forward the SCG measurementreport to the SN.
 9. The system for operating of claim 8, wherein theSCG measurement report is received at the MN on the second SRB in aULInformationTransferMRDC message.
 10. The system for operating of claim8, wherein the first SRB is an SRB3 and the second SRB is an SRB1. 11.The system for operating of claim 8, wherein the MR-DC mode is a newradio (NR)-NR dual connectivity (NR-DC) mode.
 12. The system foroperating of claim 8, wherein the MR-DC mode is an evolved universalterrestrial radio access (E-UTRA)-new radio (NR) dual connectivity(EN-DC) mode.
 13. A secondary node (SN) for operating with a userequipment (UE) using a multi-radio dual connectivity (MR-DC) mode with amaster node (MN) and the SN, comprising: one or more processors; andmemory storing instructions that, when executed by the one or moreprocessors, configure the SN to: establish, with the UE, a signalingradio bearer (SRB); while the SRB with the UE is established, receive,from the MN, a secondary cell group (SCG) measurement report for the UE;and determine, based on contents of the SCG measurement report, toperform a handover from a special cell (SpCell) of the SN to a neighborcell of a target node.
 14. The SN of claim 13, wherein thedetermination, based on the contents of the SCG measurement report, toperform the handover comprises comparing a difference between a powerlevel of the SpCell of the SN from the SCG measurement report and apower level of the neighbor cell of the target node from the SCGmeasurement report to a threshold amount.
 15. The SN of claim 13,wherein the SRB is an SRB3.
 16. The SN of claim 13, wherein the MR-DCmode is a new radio (NR)-NR dual connectivity (NR-DC) mode.
 17. The SNof claim 13, wherein the MR-DC mode is an evolved universal terrestrialradio access (E-UTRA)-new radio (NR) dual connectivity (EN-DC) mode. 18.The SN of claim 13, wherein the target node is the SN.
 19. The SN ofclaim 13, further comprising sending, to the target node, a handoverrequest.